我已经使用owin登录，但无法退出。
在开始时：

 
public void ConfigureOAuth(IAppBuilder app)
        {
   OAuthAuthorizationServerOptions OAuthServerOptions = new OAuthAuthorizationServerOptions()
            {
                AllowInsecureHttp = true,
                TokenEndpointPath = new PathString("/token"),
                AccessTokenExpireTimeSpan = TimeSpan.FromMinutes(20),
                Provider = new AuthorizationServerProvider(),
                AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie               
            };
            app.UseOAuthBearerTokens(OAuthServerOptions);
            app.UseCookieAuthentication(new CookieAuthenticationOptions());
        }

在AuthorizationServerProvider中：

 public override Task ValidateClientAuthentication(OAuthValidateClientAuthenticationContext context)
        {
            context.Validated();
            return Task.FromResult(null);
        }

        public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
        {
            context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*"});
            using (demoEntities _repo = new demoEntities())
            {
                if (!_repo.users.Where(x => x.username == context.UserName && x.pass == context.Password).Any())
                {
                    context.SetError("invalid_grant", "wrong.");
                    //context.Rejected();
                    return;
                }
            }
            //context.Request.
            var identity = new ClaimsIdentity(context.Options.AuthenticationType);
            identity.AddClaim(new Claim("sub", context.UserName));
            identity.AddClaim(new Claim("role", "user"));
            identity.AddClaim(new Claim(ClaimTypes.Name, context.UserName));
            if (context.Request.Path.Value != "/api/apidemo/logout")
            {
                context.Request.Context.Authentication.SignIn(identity);
            }
            else
            {
                context.Request.Context.Authentication.SignOut();
            }

            context.Validated(identity);
        }

在ApiController中：

  [HttpGet]
    [ActionName("logout")]
    public IHttpActionResult logout()
    {
        Request.GetOwinContext().Authentication.SignOut(DefaultAuthenticationTypes.ApplicationCookie);
        this.Authentication.SignOut(DefaultAuthenticationTypes.ApplicationCookie);
        return Ok();
    }

我调用注销然后使用旧的令牌，但它仍然可以使用。